1. Field of the Invention
The present invention relates generally to carburetors and more specifically to a straight bore butterfly valve carburetor with accelerator assist module, which enables a butterfly valve to be used for small engine applications without the problem of reverse flow.
2. Discussion of the Prior Art
Butterfly valve carburetors running on a lean fuel mixture cannot accelerate without a venturi intake chamber. However, intake chambers with a venturi exaggerate the problem of reverse flow or spit back by increasing the velocity of the reverse flow. Reverse flow occurs every time the engine makes a revolution. Gas is forced back through the intake manifold, intake chamber and into the air cleaner every time the engine makes a revolution. The present solution to the reverse flow problem is to replace the butterfly valve with a rotary valve or a sliding valve. Replacing the venturi intake chamber with a substantially straight bore intake chamber decreases the velocity of the reverse flow and greatly decreases the amount of gas forced back into the air cleaner.
Using an acceleration assist module as disclosed in U.S. Pat. No. 7,410,153 is hereby incorporated by reference in its entirety and has the unexpected result or benefit of allowing the venturi to be completely eliminated from the intake chamber of the carburetor. Further, elimination of the venturi has the unexpected result of allowing the use of a dependent fuel supply system. Fuel adjustment needles in the dependent fuel supply system are replaced with fixed jets. Fuel flows through a fixed size aperture in the fixed jet and cannot be adjusted, because the adjustment needle is eliminated. Fixed jets are well known in the art and need not be explained in further detail.
Using fixed jets instead of adjustment screws lowers the cost of the carburetor and work for an engine manufacturer. A carburetor manufacturer collects data concerning a specific engine and fine tunes the fixed jets for the specific engine. The carburetor is fastened to the specific engine without the need for manipulating adjustment needles.
U.S. Pat. No. 6,481,699 to Aihara et al. discloses an acceleration device for a two-cycle engine. The Aihara et al. patent includes an acceleration device of a carburetor for a two cycle engine with a rotary valve, which controls air flow through both a scavenging passage and a separate air intake passage each extending through a carburetor body. However, the acceleration device is connected to an air reference chamber located below a metering fuel chamber. The air reference chamber is separated from the metering fuel chamber by a diaphragm.
Accordingly, there is a clearly felt need in the art for a straight bore butterfly valve carburetor with accelerator assist module, which enables a butterfly valve without a venturi intake chamber to be used for small engine applications.